Various types of security systems to protect retail goods on display in a store are known throughout the trade. The basic components of the system include a sensor which is attached to each item of merchandise intended to be protected, a switch within the sensor which generates an alarm signal, splitter boxes or similar modular connecting units for receiving signals from the sensors, and an alarm box which is connected to the splitter boxes through various conducting cables and which houses an alarm and related circuitry.
Merchandise security systems can be broadly classified into two groups, closed loop and open loop systems. In a closed loop security system, current constantly flows from the alarm box to the sensor. The sensor switch is in a normally open state, i.e., a non-conducting state. Depressing the actuator of the switch would place the switch in a closed state, i.e., a conducting state. The sensor is attached to the article through the use of two-sided tape or a similar means. With the sensor flush against the item of merchandise, the actuator of the switch is depressed, placing the switch in its closed state, i.e. the contacts of the switch make or are electrically connected. After a sensor is attached to each item of merchandise, the alarm circuit is armed or set. When armed, the alarm box circuitry sends out a continuous current through the splitter boxes and sensor switches; the current then returns to the alarm box circuitry. As long as no cables are cut and the actuator remains depressed, the security system remains in this armed state.
During an unauthorized removal of the sensor, the actuator is distended, which opens the switch contacts and which breaks the closed loop circuit. Similarly, if a cable is cut the continuous current to the sensor is interrupted. The alarm box circuitry detects that the current has been interrupted and an alarm will sound. The alarm notifies store personnel that there has been a security breach.
A typical closed loop alarm system is disclosed in U.S. Pat. No. 5,172,098, issued Dec. 15, 1992 (the '098 patent). This alarm system includes an alarm box, multiple splitter boxes, shunt plugs for the splitter boxes, sensors, light emitting diodes (LEDs) on the sensors, switches in each sensor, and a power supply. The power supply provides power to the alarm circuitry and the LEDs. The LEDs located on the sensors are two-terminal bi-color LEDs. When the sensor is properly affixed to the merchandise, the actuator of the switch is depressed and the current flows from the alarm circuit to the detector circuit in the splitter box, through the connector cables and finally through the sensor switches. This forms a first circuit loop or a switch loop.
The detector circuit determines if the switch is closed and therefore whether the merchandise is secured. When in the armed or secured state, current flows through a second loop (the LED loop) to power the LED a first color, e.g., red. This second loop doubles the number of wires and connections requiring a total of four wires for this alarm system sensor.
The increase in the number of wires and connections increases the costs associated with these alarm systems. In addition, the increased number of loops or circuits, means that there is a greater likelihood of improper installation since inaccurate feedback may be given to the person installing the system. For example, the sensor may be improperly attached to the merchandise, but the LED may indicate an armed condition. This may occur when one loop has been damaged or when there is a faulty connection in one of the loops.
When the sensor is removed from the merchandise, the sensor switch is opened and the detector circuit determines that a security breach has occurred. The detector circuit sends a signal to the alarm circuit activating the alarm and also sends a control signal through the second loop to change the color of the sensor LED to indicate an unsecured state, e.g., green.
The '098 patent's splitter boxes typically have connections for up to six items of merchandise. The splitter boxes can be strung together to increase the number of items secured. When the number of pieces of merchandise needed to be secured is not a multiple of six, shunt plugs are required to be inserted into all open connections, to keep the sensor loop closed.
The assignee of the '098 patent has developed several security systems which operate similar to the '098 patent, for example its Kord Kontrol.RTM. strip alarm system. The assignee's variations from the '098 patent have substantially the same drawbacks as the '098 patent.
A drawback of all closed loop security systems is that current must constantly flow. Accordingly, power must be supplied to the sensor switch at all times. This presents a problem during power outages. Also, many stores turn off all power to the retail floor space at night or when the store is closed.
Battery backups have been designed to supply the necessary current; however, the current draw on the batteries is often too great to supply current for extended periods of time. This leaves the merchandise unprotected from unscrupulous security guards and support personnel (janitors, stock boys, etc.). In addition, batteries would need to be checked and replaced on a regular basis, increasing the maintenance of the security system. Recently, the situation has become more acute with the use of light emitting diodes (LEDs) on the splitter boxes and on the sensors. The LEDs add to the current drain making a battery back-up system an even less viable option.
Another drawback to many closed loop security systems is that they require shunt plugs on the splitter box connections which are not connected to merchandise. The shunt plugs form an electrical connection to prevent the alarm from sounding when the system is armed. Shunt plugs increase the cost of the system and are also a source of misconnections if improperly installed. Further, shunt plugs must constantly be installed and removed as the items of merchandise are sold or as stock is replaced. Accordingly, the shunt plugs increase the amount of time store personnel must spend attending to the security system. In addition, if the required shunt plugs are lost or not installed properly the security system is inoperable since the alarm will sound continuously.
An open loop security system operates in a similar fashion to a closed loop system. However, the sensor switch would be normally closed, i.e. when the actuator is distended. When the sensor is properly attached to the merchandise, the actuator is depressed and the circuit is open. If there is a tampering of the sensor switch, the actuator distends, the switch contacts close and current flows through the sensor switch. A circuit is completed when the sensor switch closes, activating the alarm.
In an open loop security system, the alarm does not sound unless a circuit is completed. Normally, the only way to complete the circuit is to remove the sensor from the article. Therefore, an open loop security system may be circumvented by cutting the sensor cable or removing the sensor cable plug from its jack. In this manner, the article may be stolen without the alarm sounding. Since open loop systems are easier to circumvent, they are not as popular as closed loop systems.
In both, closed loop and open loop systems, the use of alarm modules or splitter boxes increases the maintenance of the security system. Extra connections are required to incorporate these splitter boxes; these extra connections are a weak link that can be attacked by a thief. Further, splitter boxes are unsightly to look at, and are a source of misconnections and false alarms.